The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show th...The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show that PC strengthens the migration of boundaries,and then the twin grains,most of which distribute in the coarse grains,“spheroidize”to equiaxed grains,thus separating the coarse grains and refining the microstructure.This process homogenizes the initial microstructure and eliminate the typically lamellar twin grains.Moreover,PC also strengthens the dislocation annihilation.When the specimens were annealed by PC at 300℃for 4 min,the dislocation density was even lower than that annealed by furnaces at 400℃for 3 h before deformation.Furthermore,dislocation annihilation is enhanced with the increase of peak current density and the decrease of pulsed frequency.展开更多
In this paper, Ta/[NiFe（15 nm）/FeMn（10 nm）]/Ta exchange-biased bilayers are fabricated by magnetron sputtering, and their static and dynamic magnetic properties before and after rapid annealing treatment with puls...In this paper, Ta/[NiFe（15 nm）/FeMn（10 nm）]/Ta exchange-biased bilayers are fabricated by magnetron sputtering, and their static and dynamic magnetic properties before and after rapid annealing treatment with pulsed current are charac- terized by using a vibrating sample magnetometer （VSM） and a vector network analyzer （VNA）, respectively. The exchange bias field He and static anisotropy field Hksta decrease from 118.45 Oe （10e = 79.5775 A.m-1） and 126.84 Oe at 0 V to 94.75 Oe and 102.31 Oe at 90 V, respectively, with increasing capacitor voltage, which supplies pulsed current to heat the sample. The effect of flash thermal annealing by pulsed current on the rotational anisotropy （Hrot）, the difference value between static and dynamic magnetic anisotropy, is investigated particularly. The highest Hrot is obtained in the sample annealing with 45-V capacitor （3300 μF） voltage. According to the anisotropic magnetoresistance measurements, it can be explained by the fact that the temperature of the sample is around the blocking temperature of the exchange bias system （Tb） at 45 V, the critical temperature where the formation of more unstable antiferromagnetic grains occurs.展开更多
基金Project(51635005)supported by the National Natural Science Foundation of China
文摘The annealing tests heated by pulsed current(PC)or furnace for AZ31B magnesium sheets were carried out,and the effects of PC on the microstructure and dislocation density of the alloy were analyzed.The results show that PC strengthens the migration of boundaries,and then the twin grains,most of which distribute in the coarse grains,“spheroidize”to equiaxed grains,thus separating the coarse grains and refining the microstructure.This process homogenizes the initial microstructure and eliminate the typically lamellar twin grains.Moreover,PC also strengthens the dislocation annihilation.When the specimens were annealed by PC at 300℃for 4 min,the dislocation density was even lower than that annealed by furnaces at 400℃for 3 h before deformation.Furthermore,dislocation annihilation is enhanced with the increase of peak current density and the decrease of pulsed frequency.
基金Project supported by the Young Science and Technology Innovation Team of Sichuan Province,China(Grant No.2017TD0020)
文摘In this paper, Ta/[NiFe（15 nm）/FeMn（10 nm）]/Ta exchange-biased bilayers are fabricated by magnetron sputtering, and their static and dynamic magnetic properties before and after rapid annealing treatment with pulsed current are charac- terized by using a vibrating sample magnetometer （VSM） and a vector network analyzer （VNA）, respectively. The exchange bias field He and static anisotropy field Hksta decrease from 118.45 Oe （10e = 79.5775 A.m-1） and 126.84 Oe at 0 V to 94.75 Oe and 102.31 Oe at 90 V, respectively, with increasing capacitor voltage, which supplies pulsed current to heat the sample. The effect of flash thermal annealing by pulsed current on the rotational anisotropy （Hrot）, the difference value between static and dynamic magnetic anisotropy, is investigated particularly. The highest Hrot is obtained in the sample annealing with 45-V capacitor （3300 μF） voltage. According to the anisotropic magnetoresistance measurements, it can be explained by the fact that the temperature of the sample is around the blocking temperature of the exchange bias system （Tb） at 45 V, the critical temperature where the formation of more unstable antiferromagnetic grains occurs.
